I don't want to argue statistical methodology, and I'm the first to say that ten incidents is not enough to establish a trend or a statistical probability. However, my school has a lot of private citizen students who are involved in shootings. At the Tactical Conference this year I gave a Power Point presentation on ten representative incidents from our files. They are just that-- typical examples of private citizen self defense shootings. Here are a few tidbits from the summary.

5 of the 10 incidents involved an armed robbery by 1 or 2 suspects.
3 occurred on mall parking lots, only 1 occurred in the student's home.
The lowest number of shots fired was 1. The highest was 11. The average was 3.8. There were 3 cases which involved 4 or more shots.

In 2 cases, the defender fired 8 and 11 shots. These were above the average, and neither would have been able to do that with a five shot gun.

Here is my take on "averages". If you have one foot in a campfire and one foot on a block of ice, on average you're comfortable. Since needing more than 4-5 shots is a reasonably forseeable problem, I carry a gun that holds more BB's. YMMV